The lens is dependent for its survival on intercellular communication mediated by physiologically and structurally distinct gap junctions at three different sites: lens epithelial-to-epithelial cell, epithelial-to- fiber cell, and fiber-to-fiber cell. Studies in other systems have shown that there is a family of related gap junction proteins or connexins each containing conserved and unique domains. Experiments proposed will identify cDNA clones for the connexins expressed by the chick embryo lens. Those cDNAs will be fully sequenced and the protein structures predicted. Lens connexin-specific antisera will be raised to unique synthetic peptide sequences. Those antisera will be used to identify the components of the three different lens gap junctions by immunofluorescent and EM immunocytochemical localization. Expression of mRNAs derived from the cloned connexin cDNAs in paired Xenopus oocytes will demonstrate their competence to form communicating gap junctional channels, will investigate unique lens connexin physiologies, and will establish the relation of those physiologic features to structure. The cDNA and antibody probes will be utilized in a chick embryo lens tissue culture system to investigate the differentiation, biochemistry, and regulation of lens gap junctions. Northern blotting experiments will examine the developmental control and cell-type specificity of connexin mRNA expression. Immunoprecipitation will be used to examine connexin synthesis and post- translational modifications and the assembly and degradation of gap junctions. These studies will develop reagents crucial for understanding the role of intercellular communication in lens biology and cataract formation. They will also approach central questions in gap junction biology including: Can one cell (the lens epithelial cell) simultaneously make more than one gap junction protein? How does one cell form different gap junctions with two different cellular neighbors (epithelial-epithelial and epithelial-fiber cell)? How are gap junctions assembled, modified, and regulated?